Can I use the Arduino as a standalone chip? Do I need any additional components?
After I program the chip, can I remove it from its DIP socket, buy another crystal and plug them in?
I also need to be able to run it on 9v of power. What is the best solution? I really need to bring it down to the circuit board level.
Any other options?
Yes to all! Refer to this wonderful tutorial from NYU:
The answer to the What question is also in the tutorial. The 7805 voltage regulator will take 9V and drops it to 5V.
The 7805 voltage regulator will take 9V and drops it to 5V.
That’s the easiest solution (might be the cheapest, too); but whether it will work for the application will depend on a number of things. Depending on the circuit, it may be better to use a different “low dropout” regulator, or possibly one of the switching regulator “drop in” components (note that these aren’t very cheap, comparatively; they run about $15.00 USD - but they are rather nifty).
Just something to keep in mind; you may want to prototype your circuit with the 7805 and a 9 VDC wall wart, and note the current draw; if it seems high for your final implementation (let’s say you are figuring to use a 9V battery) - then an LDO regulator or such might better fit the bill (rather than wasting the current with the excess 4 volts being “wasted” as heat by the 7805).